Aluminium Foil and Remote Car Keys: Protection Against Modern Car Thieves

There is a very serious issue behind it.

At first glance, it may seem like an odd internet hack. Yet anyone who unlocks their car with a remote key or starts it at the press of a button is a popular target for modern car thieves. A small sheet of aluminium foil can significantly reduce this vulnerability - provided you understand how the trick works and what further precautions are needed.

Remote keys often make things far too easy for thieves

Keyless systems have made everyday life more convenient: the key stays in a pocket, while the car detects it automatically and unlocks or starts. Communication takes place by radio, generally on frequencies around 315 or 433 megahertz. For thieves, that is precisely what makes these systems attractive.

The most common attack method is known as a “relay attack”. It involves two offenders working together:

• One stands close to the front door or flat door, where the key is lying in the hallway.
• The other waits beside the car.
• Using a signal-amplifying device, they extend the key’s radio signal.
• The car “believes” the key is immediately nearby - the doors unlock and the engine starts.

Nobody needs to touch the original key; it remains inside the property. On a driveway or street, everything appears to be an entirely ordinary starting procedure. Many victims do not realise their car has gone until the following morning.

Another technique uses so-called signal or code grabbers. These record the radio communication when a driver unlocks or locks the vehicle, then attempt to misuse that data later. Such devices are becoming cheaper and are relatively easy to obtain through indirect channels.

“Thieves no longer need a screwdriver today - a radio signal amplifier is enough to steal many modern cars in just a few seconds.”

Anyone who values their vehicle should therefore not rely solely on convenience features, but should have a strategy against these digital attacks.

Why aluminium foil really shields a remote car key

The aluminium-foil trick might initially sound like advice from the tinfoil-hat brigade, but it is based on sound physics. The key principle is the so-called Faraday cage.

How the Faraday principle works

A Faraday cage is an enclosure made from conductive material - usually metal - that shields electrical and electromagnetic fields both inside and outside it. When radio waves hit this enclosure, the resulting currents travel across its surface. The space inside remains free of radio signals.

That is exactly what happens when a remote car key is carefully wrapped in aluminium foil:

• Aluminium conducts electricity extremely well.
• Radio waves are reflected by the foil or travel along its surface.
• The signal can no longer pass from the inside to the outside - or the other way round.

The key can therefore no longer transmit or receive a radio signal. Signal amplifiers and code grabbers then simply have nothing to intercept.

“When used correctly, a piece of aluminium foil creates complete radio silence - making the key virtually invisible to car thieves.”

How to wrap the key properly

For the protective effect to work, a half-hearted attempt is not enough. A few straightforward but important steps make the difference:

• Wrap the entire key, including its plastic casing, without leaving any gaps.
• Use two or three layers of foil to compensate for tiny tears or creases.
• Press down the edges firmly so that no openings remain.
• Test it straight away: ideally, stand close to the car and try to unlock the doors or start the engine.
• Replace the foil regularly, as it can tear and become creased over time.

Ordinary household aluminium foil is generally sufficient to greatly reduce the common frequencies used by remote car keys. The shielding works regardless of make or model - whether it is a small car, SUV or executive vehicle makes no difference.

For a more convenient and durable option, you can choose dedicated RFID protective pouches or boxes. They use the same Faraday principle, but look neater and are more robust. However, they cost more than a piece of kitchen foil.

Where your car key should really be kept at home

The place where the key is stored at home matters more than many people realise. If it is left right beside the front door, burglars may need only to walk past briefly with technology in a backpack.

Sensible rules at home include:

• Do not keep keys near external walls, windows or front doors.
• Store them as close to the centre of the flat or house as possible.
• Use a metal container, such as a sturdy tin or small metal box.
• Make sure every family member follows the same storage routine.

In households with several cars, one forgotten key on the coat stand is enough to undermine every other precaution. Establishing a fixed routine - for example, putting all keys into a metal box further inside the hallway after arriving home - noticeably reduces the risk.

Why combining security measures makes most sense

Aluminium foil or an RFID box addresses a key weakness, but neither is a cure-all. Ideally, anyone seeking to protect a vehicle should use several layers of security.

Traditional deterrents still work

Mechanical devices may be seen as old-fashioned, but they remain surprisingly effective. Typical options include:

• A steering-wheel lock or pedal lock
• Visible alarm systems, flashing LEDs and stickers
• Parking in well-lit, busy locations rather than dark corners

Thieves always look for the easiest option. Simply suggesting extra effort or noise is often enough to make them move on to the next, less well-protected car.

Using electronic aids properly

Many cars come with sophisticated security technology as standard: immobilisers, tilt and interior sensors, and GPS trackers. The problem is that hardly anyone ever checks whether these systems are still working correctly.

A quick inspection at a garage or by an automotive electrician usually costs little, but can reveal faults or incorrect settings. Anyone who travels frequently or lives in an area with a high theft rate can have an additional GPS tracker fitted. This improves the chances of recovering a stolen vehicle.

Many manufacturers now also allow the passive keyless function to be disabled in the settings. The car can still be unlocked by radio, but the purely proximity-based start without actively pressing a button is removed. Anyone willing to sacrifice that extra convenience can virtually eliminate the classic relay attack.

What the technical terms mean - briefly explained

Specialist radio-technology terms frequently arise in discussions about car theft. Two in particular are especially common for drivers.

• RFID: This stands for “Radio-Frequency Identification”. It refers to small chips that can be read by radio - the technology is used in modern car keys, bank cards, identity documents and much more.
• Faraday cage: A metal enclosure that blocks radio waves. A car itself already acts partly as this kind of cage, but radio signals for convenience functions are deliberately allowed in and out - which is exactly what thieves exploit.

Understanding these basics makes it much easier to judge new security advice and reduces the likelihood of falling for pointless or overpriced products.

Practical examples: everyday security with a remote car key

A realistic level of protection can be achieved through a few established habits that quickly become second nature. One possible daily routine is:

• While out: Keep the key in a trouser pocket or handbag, not on a café table.
• When refuelling or shopping: Keep an eye on the car, lock it deliberately, and briefly check that the doors are genuinely secured.
• On arriving home: Take the key out of your jacket, place it in aluminium foil or a protective pouch, and put it straight in its designated storage place.
• Once a month: Check that the alarm system works, check the key battery level, and replace the foil.

Anyone who also disables the passive keyless function and uses visible mechanical security devices makes their vehicle unattractive to most offenders. Crime can never be prevented entirely, but these steps greatly increase the effort required even for professionals.

The bottom line is that the convenience of keyless systems comes at a price, but drivers are not powerless. A few seconds spent with a piece of aluminium foil, clear key-storage habits at home and a handful of well-considered security measures substantially reduce the risk - and make it highly likely that the car will still be where it was parked the previous evening when morning comes.